Site-specific intravascular ultrasound analysis of remodelling index and calcified necrosis patterns reveals novel blueprints for coronary plaque instability

Post-mortem pathological studies have shown that a “vulnerable” plaque is the dominant patho-physiological mechanism responsible for acute coronary syndromes (ACS) (1-3). However, despite this knowledge, we have not yet reached a stage in our diagnostic ability where we are able to predict an event. One way to image plaques in vivo is by using histological “surrogates” created by intravascular ultrasound derived virtual histology (IVUS-VH) (4). IVUS-VH has been validated in human pathological studies and atherectomy specimens and is based upon the analysis of ultrasound backscatter as different plaque components produce a particular spectrum (5-7). The power, amplitude and frequency of the signal undergo de-convolution through a trained classification tree. This process transforms signals into four colour-coded pixels: fibrous (green); fibro-fatty tissue (light green); necrotic core (red) and dense calcium (white). This has been found to correlate with histopathology and atherectomy specimens (predictive accuracy =87.1%, 87.1%, 88.3%, and 96.5% for fibrous, fibro-fatty, necrotic core, and dense calcium, respectively) (5-7)